I noticed the new securityProbe5E has a jumper in the back, what is this used for?

AKCPsecurityProbe Series, Support

AKCP securityProbe5E Modbus Jumper – what is it for? That jumper is a 120 ohm switch, as in some cases of Modbus integration 120 ohms is needed on the RS485 input, so that has been added.

AKCPI noticed the new securityProbe5E has a jumper in the back, what is this used for?